A liquid crystal display (LCD) device includes an LCD panel and a backlight unit that provides a light source for the LCD panel, where the backlight unit includes a light emitting diode (LED) backlight driving circuit. As shown in FIG. 1, the LED backlight driving circuit includes a power supply, an LED light bar coupled to an output end of the power supply, and a constant current driving chip that drives the LED light bar to light. When voltage of the LED backlight driving circuit decreases, output current of the power supply increases, which easily damages components of the LED backlight driving circuit. Thus, an under-voltage protection pin of the constant current driving chip avoids voltage damages to the components of the LED backlight driving circuit, where the under-voltage protection pin detects an output voltage of the power supply. When voltage of the under-voltage protection pin is less than a trigger voltage of an inside of the constant current driving chip, the constant current driving chip performs a protection function, which allows an entire LED backlight driving circuit to stop working.
A typical LED constant current driving chip has only a function of under-voltage protection, when an input voltage of the constant current driving chip is too great, namely exceeds a range accepted by the constant current driving chip, which damages the constant current driving chip and affects the entire LED backlight driving circuit.